1.0 Purpose
To reinforce the chassis of MSXIV the team is looking into the adding sheet metal to gain the extra structural support needed. This page seeks to find all possible consideration to this addition to the car. Considerations such as relevant regulation from the American Solar Car Challenge (ASC), different sub-assemblies within MSXIV that may interfere with the addition, and ways to go about adding it to the car.
2.0 Relevant Regulations
This section will list the important regulations that will be relevant to the attachment of sheet metal.
9.3 - Ground Clearance
The fully-laden solar car must have a minimum ground clearance of 50 mm such that he solar car can be driven over a 50 mm object and no part of the solar car except for the tire may make contact with the object.
Ground clearance of 50mm
10.3.D - Belly Pan
The cockpit must be equipped with a full belly pan to isolate the occupants from the road. The belly pan be strong enough to support the full weight of each occupant. Each occupant’s torso and limbs must be above the lower element of the structural chassis.
Belly pan must be strong enough to support the full weight of each occupant
10.4 - Fastener
All fasteners must be of suitable type, strength, and durability for their application. Friction, glued, or press fit assemblies will not be accepted in critical areas (as defined in 10.4.E) as the sole means of retention. For glued of press fit assemblies a pin is required. The pin diameter shall be 1/4 of the tube’s outer diameter. A press fit roll pin is acceptable for this application. Set screw intended to transmit torque of force will not be accepted.
10.4.A - Bolts
Bolts used in critical areas (as defined in 10.4.E) must at minimum meet SAE grade 5, metric grade M*.* and/or AN/MS specifications. Bolts must be of the correct length, and extend at least two threads beyond the nut. Bolts in tension must not have shave or cut heads. All fasteners should be a properly torqued. U-bolts are not allowed in critical areas.
Must be correct length, extend two threads beyond nut, don’t shave or cut heads of bolts.
10.4.B - Securing of Fasteners
All structural and other critical fasteners (bolts, nuts) must have an acceptable form of securing such that the fastener cannot loosen of be removed unintentionally. Acceptable methods of securing are:
(1) Bolts with flex-loc type nuts or other nuts that use flexure as the means of locking and are re-useable.
(2) Bolts with pre-drilled shafts and castle nuts with cotter pins installed to prevent loosing.
(3) Bolts with pre-drilled heads and/or nuts properly safety wired with stainless steel wire from 0.024” (0.6 mm) to 0.032” (0.8 mm) diameter conforming to Mil Spec MS20995C. The safety wire between fasteners and anchor points must be twisted to prevent rotation of the fastener.
(4) In blind hole applications, bolts with pre-drilled heads properly safety wired.
(5) Other methods of securing fasteners may be deemed acceptable at the discretion of the Inspector.
Securing methods that are not acceptable are Nylon lock nuts, “lock” washers, Loctite, or lock nuts that use thread distortion as a means to secure the nut. Lock nuts with thread distortion are not considered to be reusable. Other methods of securing fasteners, where the above methods are not appropriate may be considered at the discretion of the Inspector. Non-critical fasteners need not be secured with lock nuts.
Don’t use nylon lock nuts, “lock” washers, Loctite, or lock nuts that use thread distortion. Also make sure it cannot be unintentionally undone.
10.4.E Critical Areas
For application of the above critical areas are defined to include: steering, braking, suspension, seat mounts, safety harness, drive train, battery box, and ballast carrier.
No critical areas so long as reinforcements don’t interfere with seats, seatbelt mounts, catamaran cover or the ballast boxes.
3.0 Potential Sub-assembly Interferences
As this project was started from changing the bottom panel from a structural member to a non-structural one, there will be a focus on the assemblies that will be near the bottom panel.
Slide | Sub-Assembly | Details | DRI |
|---|---|---|---|
15 | Catamaran Cover | Top of the catamaran from between the A and B-plane to C-plane | Renzo |
16 | Seats | On the floor between the A and B-planes, and between the B and C-planes | Asher |
19 | Dashboard | On the catamaran tube between the A and B-plane. | Renzo on slide deck I believe Ali is taking it on now though |
22 | Floor Panels | Bottom members of the chassis between A and C-planes. | Isha on slide deck Michael Hanley on Mech Check-In |
27 | Seatbelt Mounts | Specifically the ones mounted to the floor between the A and B-plane, and the ones between the B and C-plane. | Filip |
32 | Rear Brake Lines | On the bottom of the catamaran on the driver’s side | Geoffrey |
Sourced from the Chassis Mounting Reservation Slide Deck
4.0 Sheet Metal Mounting Designs
During the manufacturing process the final product may not match the original design as intended; the product will not match the CAD perfectly. This section will look at different ways to secure the sheet metal to the chassis while following different regulations and passing simulations.
Some thoughts:
To prevent stress from accumulating on certain chassis members, it might be worth looking into increasing the surface area the sheet metal will be attached to the chassis with. Specifically, look into attaching the sheet metal to multiple sides of the square tubing.
Spacers or shims can be added to fill in gaps from CAD inaccuracies, but the chassis would need to be cut if an intersection becomes apparent. Better to design with the intent of adjusting the amount of gap; leave room in the current CAD between chassis members and sheet metal.
5.0 Random Thoughts
Since the bottom panel is getting reinforced, as well as the chassis, might there be a way to solve both with a single solution?